<div class="row form-group">
  <div class="col-sm-6">
    <div class='form-group'>
      <label class="col-sm-3 control-label">Fecha:</label>
      <div class="col-sm-3">
        <input type='text' class='form-control fecha' name='f_txt_fecha' placeholder='Fecha'>
      </div>
    </div>
  </div>

  <div class="col-sm-6">
    <div class='form-group'>
      <label class="col-sm-3 control-label">Horas:</label>
      <div class="col-sm-3">
        <input type='text' class='form-control' name='f_txt_horas' placeholder='Horas'>
      </div>
    </div>
  </div>

  <div class="col-sm-6">
    <div class='form-group'>
      <label class="col-sm-3 control-label">Detalle de la actividad:</label>
      <div class="col-sm-6">
        <input type='text' class='form-control' name='f_txt_detalle_actividad' placeholder='Descripción'>
      </div>
    </div>
  </div>
</div>